Jobs for April: Trees and shrubs

Planting and moving

Evergreens

In cooler areas, and earlier in the month, you can still move and plant evergreen trees and shrubs (see Elaeagnus × ebbingei ‘Limelight’, pictured), provided the soil is not waterlogged or dry. They are best moved or planted once actively growing and when there is less risk of cold weather.

Deciduous

In colder areas, you can also still plant container-grown deciduous hedging plants, shrubs, trees and climbers. Stakes and plastic-free biodegradable rabbit guards should be put in place at the time of planting to prevent damage to the rootball and bark.

Remember that watering and establishment may be problematic for large plants as the weather gets warmer and dryer, and you may be better delaying planting these until October.

Feeding and mulching

Mulch rose and shrub beds with a 5-8cm (2-3in) layer of organic matter. This will help retain moisture during dry spells, reduce weeds and over time improve soil structure. Pay particular attention to mulching around rhododendrons, azaleas and camellias, as flowering is impaired if they dry out during late summer.

Only young, weak, damaged or heavily pruned trees, shrubs and hedges will need feeding. Feed with a general fertiliser (such as seaweed or blood, fish and bone), sprinkling it over the root area before hoeing into the soil surface. 

Pruning and training

Shrubs with colourful winter stems such as willow (Salix) and dogwood (Cornus) can still be cut back at the beginning of the month. Prune back hard all the previous year’s growth to within 1-2cm (0.5-0.75in) of the framework.

Other shrubs that are routinely stooled (cut back hard) in spring to keep their larger or more brightly coloured juvenile foliage, such as the smoke bush (Cotinus) and elders (Sambucus), can be cut back this month. You can leave some branches as they are if you are reluctant to lose all the height gained last year.

Delay pruning spring-flowering shrubs such as Forsythia and Chaenomeles until after they have finished flowering, otherwise this year’s display will be lost.

Remove any frost-damaged shoots from evergreens affected by earlier cold weather.

Remove any reverted green shoots on hardy variegated evergreens, to prevent reversion taking over.

Lightly cut back lavenders to stop them getting too leggy and woody. Treat Helichrysum (curry plant) and Santolina (cotton lavender) similarly.

Loosen any tree ties that are digging into the bark, or could do so soon as the trunk girth expands.

Twining climbers (such as honeysuckle and clematis) need regular tying in with twine and wrapping around their supports.

Tie in climbing and rambling roses with twine, as near to horizontal as possible. This will restrict sap flow, causing more sideshoots to grow along the stems, and so producing more flowers.

Problems

Bracket fungus (pictured) on trees is more visible at this time of year. If the tree is in poor health it is worth calling in a tree surgeon for a professional opinion.

Phytophthora root rots can cause dieback on mature trees and shrubs. Wet winter weather and poorly drained soils are likely to encourage this problem on susceptible woody plants.

Check for damage or cankers on deciduous trees.

Put plastic-free biodegradable rabbit guards around newly planted trees and shrubs to protect the bark.

Avoid planting new roses in areas where roses were previously growing otherwise the new plants may suffer from rose replant disease.

Inspect sick-looking box and holly trees for signs of blight.

Be aware that insects emerge as temperatures rise. Caterpillars, aphids, and other insects may start to become more apparent during mild spells. Tolerate where possible as they provide food for young fledgings, and just remove by hand where really needed.